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Full text of "Alaskan glacier studies of the National Geographic Society in the Yakutat Bay, Prince William Sound and lower Copper River regions"

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288                                 ALASKAN GLACIER STUDIES
to call attention to the possibility of explaining them by earthquakes. There is, however, one very notable difference between the oscillations of Columbia Glacier, and the advance of the Yukatat Bay glaciers in response to the 1899 earthquakes. The latter advanced spasmodically and rapidly, they were transformed in a few months' time, and the advances were short lived; the Columbia Glacier has moved more slowly, continuing its advance a longer time and gradually increasing its. rate of forward movement from nine-tenths of a foot a day in 1908 to 2rfr feet a day in 1910. This less abrupt change is more like that of the glaciers in regions like the Alps, where climatic fluctuation is assigned to explain the advances and retreats. Even this difference, however, need not eliminate the earthquake theory, for the rate and extent of the advance in response to earthquake shaking would normally vary with the intensity and duration of the shaking, as it would with variation in the amount and duration of a climatic change. Such spectacular response as has been shown by the Yakutat Bay glaciers is hardly to be commonly expected. We believe the earthquake theory a possible and rational explanation of the recent fluctuations of Columbia Glacier front; but, as between it and the climatic theory, we have no facts upon which to either eliminate the one or establish the other.